The present invention relates to a catalyst used for olefine polymerization and the preparation thereof. The present invention also relates to a method of polymerizing olefines by using the catalyst of the present invention.
Polyolefine is a very important category of polymeric materials. Half of the plastics are polyolefine. They are widely used in industry, agriculture, national defense, communication, transportation and human daily life. Olefines can be polymerized to form macromolecular compounds called polyolefines by using a catalyst. Therefore, catalyst is a key to the development of polyolefine industry which plays a very important role in controlling the structures and properties of polyolefines.
Although the conventional Ziegler-Natta catalysts are still widely used in the industrial production of polyolefines, they are not good catalysts for the manufacture of linear low-density polyethylenes (LLDPE). Recently, it was found that zirconocene, a representative of the metallocene catalysts, possesses very high catalytic activity to copolymerize olefines and can be used for the production of LLDPE. However, an xcex1-olefine (such as butene-1, hexene-1, octene-1, and the like) as the second monomer is required by using metallocene to catalyze the polymerization of olefine for the production of LLDPE, which complicated the process of polymerization. In 1996, Johnson in Du Pont Co. disclosed that xcex1-diimino nickel(II) could be used as an olefine polymerization catalyst (WO 96/23010). With the action of a co-catalyst of methyl aluminoxane (MAO) or modified methyl aluminoxane (MMAO), it is possible to homopolymerize ethylene. By controlling the polymerization conditions, it is possible to obtain polyethylene (PE) including LLDPE with high molecular weight, low density and desired degree of branching.
It is an object of the present invention to provide a catalyst used for olefine polymerization which is a polynuclear xcex1-diimino Ni(II). The precursor of this catalyst is a polynuclear xcex1-diimino Ni(II) complex. The polynuclear xcex1-diimine Ni(II) complex can be activated by a neutral Lewis acids such as MAO, MMAO, which then catalyze the polymerization of ethylene into high molecular weight branched polymeric materials.
The polynuclear xcex1-diimino Ni(II) complex of the present invention has the following structure: 
wherein M is Ni; X is Cl or Br, and preferably X is Br; m and n is dependently an integer from 0 to 100, and preferably m is from 1 to 20 and n is from 0 to 30 or m is from 0 to 20 and n is from 1 to 30, more preferably m is from 1 to 10 and n is from 0 to 20 or m is from 0 to 10 and n is from 1 to 20; R1 and R2 may be same or different, and is dependently H, methyl, ethyl, isopropyl or tert-butyl, preferably R1 is isopropyl and R2 is methyl or isopropyl; Y is CR3R4, wherein R3 and R4 may be same or different, and is dependently H, methyl, ethyl, propyl, butyl or phenyl, preferably R3 and R4 are the same, and are H or methyl, or R3 and R4 forming a cyclohexyl group; R5 and R6 may be same or different, and is dependently methyl, ethyl or heterocyclic group (such as 2-pyridyl group), preferably R5 and R6 are the same, and are methyl; Q is a divalent residual represent by the following formula or a mixture thereof: 
preferably Q is a divalent residual of the following formula: 
The polynuclear xcex1-diimino Ni(II) complex of the present invention can be prepared by a method comprising the following steps:
(a) condensing an xcex1-diketone represented by the formula or a mixture thereof, 
wherein, Q, R5 and R6 are as defined above,
a substituted aromatic diamine represented by the formula 
wherein, R1, R2 and Y are as defined above,
and a substituted aromatic amine represented by the formula 
wherein, R1 and R2 are as defined above, in a medium of alcohol, aromatic hydrocarbon, alcohol-ether mixture, or alcohol-halogenated hydrocarbon mixture and under the catalytic action of HCOOH, CF3COOH or HX, wherein X is F, Cl, Br, or I;
thereby obtaining an oligomer of substituted xcex1-diimine of the formula 
wherein, R1, R2, R5, R6, Q, Y, m and n have the same definition of above;
(b) carrying out coordination reaction of the oligomer of step (a) with NiX2, wherein X is Cl or Br, in the absence of water and oxygen, thereby obtaining a polynuclear xcex1-diimino Ni(II) complex of the following formula: 
wherein, R1, R2, R5, R6, Q, Y, M, X, m and n have the same definition of above.
The reaction process can be represent by the following scheme: 
wherein, R1, R2, R5, R6, Q, Y, M, X, m and n have the same definition of above.
The polynuclear xcex1-diimino Ni(II) complex of the present invention is capable of catalyzing the polymerization of ethylene under the action of neutral Lewis acid such as MAO or MMAO and the like. Thus, polyethylene with high molecular weight can be obtained.